What Do I Use to Replace the Asphalt Slump on My Built Up Residential Roof?

Slumping Asphalt

• An asphalt slump consists of an area in an asphalt surface that sits below the level of the rest of the surface, like a ditch or shallow hole. On a built-up roof, asphalt slumps usually occur as a result of exposure to prolonged, direct sunlight, which causes asphalt to get so hot that it becomes liquid. When it becomes liquid, asphalt loses its rigid shape and slumps. When replacing a slump, always remove all slumping asphalt completely before installing a new layer. If you plan on using a fix product on your slump, removal may not be necessary.

Rebuilding the Area

• Built-up roofs contain alternating layers of hot liquid asphalt and sheets of solid, fiberglass-reinforced or polyester-reinforced asphalt, also known as reinforced, or modified, bitumen. The hot asphalt provides the weatherproofing layer while the solid asphalt provides a solid support for the liquid asphalt . You can replace an asphalt slump by removing all layers of built-up material that are part of the slump and replacing them with new layers. Hot asphalt is applied with a mop, and is very hot. Always wear heavy boots when working with this material. Replacing a slump in this way may require removing areas of roof around the slump. If the project covers large parts of your roof, contact a roofing contractor for assistance.

Alternative Systems

• Two alternatives to built-up asphalt exist, modified bitumen systems and cold applied systems. In order to replace slumping asphalt with either of these systems, you must remove the existing built-up roof completely and replace it with a new type of roof. Modified bitumen systems consist of two layers of modified, or reinforced, bitumen. The bottom layer is smooth, and the top layer is grainy and imbued with minerals. Bitumen, a term largely synonymous with asphalt, is a naturally occurring material commonly used as an adhesive. To apply the top layer to the bottom layer in a modified bitumen system, you use a torch to melt the two together. Cold applied systems work in a similar manner, with two layers of material. However, installing cold applied systems requires no heated elements. These systems employ adhesives and coatings that are applied in a cold liquid state and harden to form bonds.

Fixes

• Some roofing companies produce materials you can use to fix slumps without replacing them. These products generally assume the form of materials that cover a slump with a hard surface. Such coatings are applied cold and wet, like cold applied roofing systems, and harden to form a solid surface over your slump, or as a single hard piece of material. Using a fix won't get rid of your slump; it just covers it up. If your asphalt slump presents no structural problems and causes no leaking, fixes can save you a good deal of money and time. However, if your slump leads to leaks or other problems with your roof or ceiling, you should replace it, rather than fix it.